What are aluminium composite panels?
Aluminium composite panels are flat facade sheets built from two thin aluminum skins bonded to a solid core. Architectural skins measure 0.5 mm on each face and use 3003 or 5005 aluminum alloy. Finished panel thickness is normally 3 mm, 4 mm or 6 mm. Building codes file the product under metal composite material (MCM), regulated by the International Building Code.
The core decides almost everything that matters. Aluminum skins behave the same way in every grade: they resist corrosion, hold a factory coating and add stiffness. The filling between them sets fire class, weight, price and fabrication method. Three core grades dominate the market: PE, FR and A2.
Standard sheet widths are 1220 mm and 1500 mm, with lengths cut to order. Factory coatings split into two families: PVDF (polyvinylidene fluoride) for exterior architectural work and polyester for interior panels and signage. Coating choice is independent of core grade, so a PVDF finish says nothing about fire performance.
How do PE, FR and A2 cores differ?
PE, FR and A2 name three levels of mineral content inside the same sandwich construction. Mineral filler replaces combustible polymer, so a higher filler share means a lower fuel load. The filler is normally aluminum trihydroxide, a white powder that releases water vapor above about 180 degrees Celsius. That reaction absorbs heat and slows flame spread.
PE core (polyethylene)
PE cores are solid low-density polyethylene with no mineral filler at all. Polyethylene softens near 110 degrees Celsius and releases high heat when it burns, so the grade carries no limited combustibility rating. PE panels are the lightest and the cheapest of the three. Their remaining role covers interior lining, retail fascia, signage and low-rise work where codes allow combustible cladding.
FR core (fire retardant)
FR cores blend polyethylene with roughly 70% mineral filler by weight. The blend still contains polymer, so FR is a fire retardant grade rather than a limited combustibility grade. The usual European classification is B-s1,d0: combustible, slow to contribute, with little smoke and no flaming droplets. FR panels serve mid-rise facades where the wall assembly passes the required full-scale test.
A2 core (limited combustibility)
A2 cores raise mineral content to about 90% and leave only a thin polymer binder. The classification is A2-s1,d0 under EN 13501-1, the European standard that grades reaction to fire. A2 also sets a hard material threshold: gross heat of combustion at or below 3.0 megajoules per kilogram. A2 panels are the heaviest and most expensive grade, and the default on tall buildings.
Core grade comparison table
Core grade selection changes several measurable properties at once. Weight figures below come from manufacturer data sheets for 4 mm aluminium composite panels with 0.5 mm skins.
| Property | PE core | FR core | A2 core |
| Core composition | Low-density polyethylene | Polyethylene with mineral filler | Mineral core with polymer binder |
| Mineral filler share | None | About 70% by weight | About 90% by weight |
| EN 13501-1 class | No limited combustibility rating | B-s1,d0 typical | A2-s1,d0 |
| Heat of combustion limit | Not capped | Not capped | 3.0 MJ per kg |
| Weight, 4 mm panel | About 5.5 kg per square meter | About 7.6 kg per square meter | About 8.5 kg per square meter |
| Typical use | Interior, signage, low-rise | Mid-rise facades | High-rise facades |
| Relative cost | Lowest | Middle | Highest |
Which fire tests separate the grades?
Fire tests fall into two groups: material tests and assembly tests. Material tests measure the panel or its core in isolation. Assembly tests burn a full wall mock-up with insulation, cavity and fixings in place. Core grade is a material property, but code approval rests on the assembly result.
ASTM E84, the Steiner tunnel test, measures surface burning and reports a flame spread index plus a smoke developed index. Class A requires a flame spread index of 25 or less and a smoke developed index of 450 or less. The method exposes the panel face, and an aluminum face resists surface spread whatever sits behind it. A Class A result therefore says little about the core.
NFPA 285 closes that gap. The method burns a two-story wall assembly for 30 minutes and records vertical and lateral fire propagation. The report belongs to the tested assembly, not to the panel alone: changing the insulation, the barrier or the cavity depth ends the listing. European practice uses EN 13501-1, supported by the single burning item test EN 13823.
What do building codes in the United States require?
Building codes tie composite panel use to building height, construction type and test evidence. The International Building Code requires NFPA 285 compliance for exterior walls with combustible components in Type I through Type IV buildings taller than 40 feet. Below that line the requirements loosen, and interior applications follow separate finish rules. The authority having jurisdiction, meaning the local official who reviews the permit, makes the final call.
New Jersey adopts the International Building Code through the New Jersey Uniform Construction Code, and New York City enforces its own Building Code. Vision Art Aluminium, a Montclair, New Jersey contractor, lists aluminium composite panels alongside its curtain wall and window systems. That pairing puts core grade into the same approval package as the framing. Approval documents in both states carry the core supplier name, the thickness and the test report number.
Why did PE core panels come under scrutiny?
PE core panels drew regulatory attention after two tower fires spread through cladding. The Grenfell Tower fire in London on 14 June 2017 involved cladding panels with a polyethylene core. The public inquiry that examined the building recorded that finding (source: Grenfell Tower Inquiry Phase 1 report). The Lacrosse tower fire in Melbourne in 2014 followed a similar pattern on a smaller scale.
England restricted the material soon afterwards. The Building (Amendment) Regulations 2018 banned combustible materials in the external walls of relevant buildings above 18 meters. A 2022 amendment lowered that threshold to 11 meters. Australian states issued their own restrictions on polyethylene core cladding. United States codes kept the existing height and assembly test framework instead.
How does core choice affect weight, cost and fabrication?
Core choice moves three project numbers at once: dead load, material cost and shop labor. Moving from a PE core to an A2 core adds roughly 3 kilograms per square meter of facade. On a large elevation that difference reaches the sub-frame, the anchor spacing and the structural calculation. Mineral filled cores also wear router bits faster and tolerate tight fold radii poorly, so shops price A2 fabrication above FR work.
Fabrication follows a fixed sequence in most shops:
- Cut the sheet to panel size.
- Rout a V-groove along every fold line.
- Fold the returns into a tray.
- Rivet corner brackets and stiffeners.
- Hang the tray on the sub-frame.
Thermal movement sets the joint width. Aluminum expands about 2.4 mm per meter for every 100 degrees Celsius of temperature change, so a long panel run needs joints that absorb it. Rainscreen designs, meaning drained and back-ventilated facades, handle that movement better than sealed wet-joint systems. Core grade does not change the movement, though a brittle A2 core limits the fold radius.
What does a complete panel specification name?
Panel specifications that clear plan review name the evidence, not just the product. A line reading “4 mm aluminum composite panel, PVDF finish” leaves the core grade open and allows a substitution during procurement. The items below close that gap.
- Core grade and the core supplier name.
- Panel thickness and skin gauge on each face.
- Reaction to fire class with the standard that produced it.
- The NFPA 285 report number and the build-up it covers.
- Coating family, color system and finish warranty term.
- Joint type: open rainscreen, gasketed or wet sealed.
- Attachment method: routed cassette, rail or rivet fixed.
Test reports carry limits of their own. A report issued for a 4 mm panel does not cover the 6 mm version. A core supplier’s report does not transfer to a different supplier’s core. Panel thickness, core supplier and assembly build-up therefore travel together through approval review.
Which core grade fits which building?
Core grade tracks building height and fire strategy more closely than budget. A2 cores answer the tall-building case with limited combustibility, a capped heat of combustion and the shortest argument at plan review. FR cores hold the middle ground on mid-rise work where the assembly carries a valid full-scale test report. PE cores keep a narrow role indoors, on signage and on permitted low-rise work.
Three practical points close the comparison. Weight rises by about 3 kilograms per square meter between the lightest and the heaviest grade, which reaches sub-frame design. Surface burning results such as ASTM E84 Class A describe the face rather than the core. Changing the core supplier, the thickness or the build-up ends the test report’s validity.
This content is for general information and not code advice. Fire classifications, code editions and product test reports change over time. Project teams verify current requirements with the authority having jurisdiction and check live manufacturer test reports.
Frequently Asked Questions
What does an A2 rating mean on a composite panel?
A2 is a reaction to fire class under EN 13501-1 that marks a material of limited combustibility. An A2 core holds about 90% mineral filler and a heat of combustion at or below 3.0 megajoules per kilogram. The suffix s1,d0 adds minimal smoke and no flaming droplets.
Are PE core panels still allowed in the United States?
PE core panels stay in use in the United States under code limits rather than an outright ban. The International Building Code controls combustible components in exterior walls by height, construction type and NFPA 285 evidence. Interior and low-rise work carries lighter requirements. The local code official rules on each project.
What is the difference between FR and A2 cores?
FR and A2 differ in mineral filler content and in fire class. FR cores blend polyethylene with roughly 70% mineral filler and stay combustible, usually classified B-s1,d0. A2 cores raise filler to about 90% and reach limited combustibility. The step adds weight and cost, and it makes folding harder.
How much heavier is an A2 panel than a PE panel?
An A2 panel weighs roughly 3 kilograms per square meter more than a PE panel of the same thickness. Manufacturer data sheets list about 5.5 kilograms per square meter for a 4 mm PE panel and about 8.5 kilograms for the A2 version. That gap affects sub-frame sizing.
Which fire test matters most on a facade project?
The assembly test matters most on facade projects with combustible components. NFPA 285 burns a two-story wall mock-up with its insulation, barrier and cavity in place, so the result describes the real wall. Material tests such as ASTM E84 describe surface behavior only.
